This application claims the priority of German application 196 23 998.2-41 filed in Germany on Jun. 15, 1996, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a reforming reactor system having at least one reactor unit filled with a catalyst material and having a particle filter which is arranged in a reformate gas pipe downstream of the reactor unit, as well as to a particle filter which can be used therefor.
A system of the initially mentioned type is disclosed in U.S. Pat. No. 2,671,719. That system is used for the industrial production of a gas mixture of hydrogen and carbon monoxide. In this case, a hydrocarbon is first reacted with a metallic oxide in a reduction reaction chamber while forming carbon oxides, hydrogen, water and free metal and subsequently the pertaining suspension is fed as a column of water into a reforming reactor unit in which the desired reforming reaction takes place. The obtained reformate gas is discharged by way of a reformate gas pipe in which a cyclone filter is arranged in order to separate entrained solid particles. The separated particles are fed by way of a return pipe connected on the bottom to the cyclone filter back into a reduction reaction chamber arranged upstream of the reforming reaction unit.
Cyclone filters for a particle separation are generally known in different constructions; see, for example, German Published Patent Application DE 41 11 031 A1 as well as British Patent Documents GB 1 534 019 and GB 737 457, and German Patent Documents DE 39 34 183 C1 and DE 521 682. A multi-step particle filter, in the case of which a first step is formed by a cyclone filter and a second step is formed of sintered-metal fine filter elements, is disclosed in European Published Patent Application EP 0 580 005 A2. A filter for the particle separation, which consists of several cloth layers which are situated behind one another and have different permeabilities, is described, for example, in German Published Patent Application DE 44 17 347 A1. Another filter of this type, which is preferably used in pyrotechnical gas generators for air bags of motor vehicles, is described in German Published Patent Application DE 42 04 758 A1. As required, a ceramic paper foil which acts as a heat shield is inserted between the filter cloth layers. Another type of filter contains several perforated plates which are connected behind one another in the gas flow direction and which are constructed with hole diameters which become smaller in the flow direction and/or are arranged with openings which are offset with respect to one another transversely to the flow direction; see, for example, the German Utility Models DE 87 90 076 U1 and DE 91 02 970 U1 as well as the German Published Patent Applications DE 34 07 617 A1 and DE 39 10 554 A1. Particle filters in the form of fiber braidings are described, for example, in German Published Patent Applications DE 40 33 019 A1, DE 42 23 278 A1 and French Published Patent Application FR 2 409 079 as well as German Utility Models DE 92 18 021 U1 and DE 69 19 686.
In Japanese Published Patent Applications JP 2-120203 (A) and JP 63-129002(A), reforming reactors are disclosed, in the case of which the catalyst material is present in the reactor unit as a pellet fill which is carried by a sieve. An empty outlet space adjoins below the sieve and a reformate gas outlet leads laterally out of this outlet space, by way of which reformate gas outlet the reformate gas leaves the reforming reactor unit.
The invention is based on the technical problem of providing a reforming reactor system which is suitable particularly for reforming water vapor of methanol and which furnishes a largely particle-free reformate gas flow, as well as a particle filter which can be used for this purpose.
Certain preferred embodiments of the invention solve this problem by providing a reforming reactor system for the water vapor reforming of methanol, comprising a reactor unit with a catalyst-filled reaction space, a sieve which carries a catalyst fill charged into the reaction space, a metallic nonwoven for collecting the sieved-out fragments and dust particles which is arranged in the reaction space at a distance below the sieve designed for the sieving-out of fragments and dust particles of the catalyst fill while forming a space situated in-between which is free of metallic nonwovens and to which the a gas pipe is connected, and a particle filter arranged in the reformate gas pipe downstream of the reactor unit.
In the case of preferred embodiments of such a reforming reactor system, the reactor unit is filled with a catalyst pellet fill which is carried by a sieve by means of which pellet fragments and pellet dust particles are sieved out of the fill in that, because of their gravity, they fall downward through the sieve. For this purpose, the mesh size of the sieve is smaller than the typical dimensions of undamaged pellets and larger than the dimensions of the fragments and dust particles to be sieved through. By means of the metallic nonwoven arranged under the sieve, the fragments are caught which are sieved out through the sieve. Since the metallic nonwoven is still situated within the reaction space of the reactor unit, the collected fragments can continue to develop their catalytic effect. As another advantage, the fragments collected in the metallic nonwoven cannot clog the gas flow filter which follows. In this case, the reformate gas flow is withdrawn from the space between the sieve and the metallic nonwoven without having to flow through the metallic nonwoven. It is understood that, as desired, a reverse flow direction can also be provided in which case the gas mixture to be reformed is fed into this space between the sieve and the metallic nonwoven.
The particle filter arranged in the reformate gas pipe filters out particles which were entrained by the reformate gas generated in the reactor unit so that a largely particle-free reformate gas flow is obtained on the output side of the particle filter. During the water vapor reforming of methanol for the purpose of generating hydrogen for a fuel cell arrangement connected behind it, for example, for a fuel-cell-driven motor vehicle, it is therefore prevented that particles, for example, in the form of fine catalyst particles, are entrained by the reformate gas flow into the fuel cells and have an unfavorable effect on the catalyst materials situated there. In addition, the sieving-out and filtering-out of particles prevents clogging in the reactor unit and in the following reformate gas flow path which increases the flow resistance. A reforming reactor constructed in this fashion is also particularly suitable for a use in motor vehicles where the risk of a formation of pellet fragments and pellet dust particles is particularly high because of shaking in the driving operation.
In the case of certain preferred embodiments of the reforming reactor system, the particle filter arranged in the reformate gas pipe contains a spun steel wool netting and/or several filter steps which are serially connected behind one another. It was found that, particularly also for the mobile application of a system for the water vapor reforming of methanol arranged in a vehicle, a reformate gas flow is obtained at relatively low expenditures which is reliably purified with respect to entrained particles.
In the case of certain preferred embodiments, a reforming reactor system is further developed such that the particle filter is inserted into the reformate gas pipe with the insertion of a thermal insulation. The thermal insulation prevents undesirable thermal losses, for example, in the form of a condensing out of water on cold walls.
The reforming reactor system according to certain preferred embodiments contains a particle filter which is arranged in the reformate gas pipe such that it can be exchanged without interrupting the operation. Operational interruptions of the system because of a required exchange or a cleaning of the particle filter are therefore avoided.
In the case of certain preferred embodiments of particle filter, the respective used filter body can be exchanged without any problems and without interrupting the operation of the system in that it is pushed out of the filter housing transversely to the gas flow pipe by a newly slid in filter body. In this case, sealing devices are provided which ensure that no significant loss of gas will occur during this exchange operation.
A cyclone filter according to certain preferred embodiments contains a cyclone pot and a particle collecting pot which can be connected below it in a removable manner, as well as a closing device which, when the particle collecting pot is connected, keeps the cyclone pot open with respect to the latter while, when the particle collecting pot is removed, it keeps the cyclone pot closed. The closing device is designed such that the opening and closing movement takes place automatically with the connecting and removal of the particle collecting pot.
In the case of a cyclone filter further developed according to certain preferred embodiments, the closing device contains a closing body which, in a closing position, can be pressed elastically against the cyclone pot wall, as well as an operating element which, when the particle collecting pot is connected, presses the closing body into an opening position spaced away from the cyclone pot wall.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.